2nd year Biology notes
Homeostatis
Homeostatis
Definition
Home means same and statis means state. So the regulatory mechanism which maintained the internal environment of a organism is called homeostatis.
Important Aspects of Homeostatis
There are three important aspects of homeostatis.
- Osmoregulation
- Thermoregulation
- Excretion
Feed Back System
The check and balance system in a body is called feed back system. In a feed back system three organs are involved.
1. Receptor
The organ which receive any change in the internal environment of the body are called Receptor.
2. Effector
The central nervous system which send the message to a particular organ are called effector. Take part in particular action.
3. Central Nervous System
The receptor transfer message to a central nervous system such as brain.
Types of Feed Back System
There are two type of feed back system.
- Positive Feed Back System
- Negative Feed Back System
1. Positive Feed Back System
When there is a change in the internal environment and it is further increase by the process are called positive feed back system.
2. Negative Feed Back System
When there is a change in the internal environment and it is further decreased by the process called negative feed back system.
Osmoregulation
Definition
The regulatory mechanism which maintain the balance between water and solute context of a cell is called osmoregulation.
Osmoregulation in Plant
Due to the availability of water there are four groups of plant.
- Hydrophyte
- Halophyte
- Xerophyte
- Mesophyte
Hydrophyte
The group of plant which is grow in fresh water are called hydrophyte.
Characteristic of Hydrophyte
- The plant do not have layer of cuticle.
- The leave have stomata in the upper surface with take part in transpiration.
- The root are either absent or poorly developed.
Hydrilla, Lotus, Lily plant
Halophytes
The group of plant which is grow in marshy soil or salty soil are called halophyte.
Characteristic of Halophyte
- These plant absorb water from such a soil, which is higher salt concentration and low water potential.
- Halophyte actively absorption salt into their roots.
- In the leaves of plants salt glands are present which helps in the removal of salt and water from the body.
- Some halophytes absorb humidity by leave.
Glass wort, Cord grass
Mesophyte
The group of plant which is grow in well watered soil are called mesophyte.
Characteristics of Mesophyte
- Their roots are well developed.
- Their body is covered by a layer called cuticle.
- They contain stomata for evaporation of extra water.
- Some mesophyte excrete out water in the form of drop this process is called guttation.
Xerophyte
The group of plant which is grow in dry places such as desert are called Xerophyte.
Characteristic of Xerophyte
- Some plants do not face dry consition and produce seed are called ephemeral plant. During raining season seeds germinate.
- Their root are well develop which go deep into the soil to absorb water.
- Some plant have horizontal root on the surface to absorb rain water rapidly.
- Some plant leaves are modified into spine to prevent transpiration.
- Stem and leave covered by cuticle.
- Some plant store water in cell (succulent)
Cacuts, Euphorbia.
Excretion
Definition
The removal of harmful substance produce in the metabolic process from the body is called Excretion.
Excretion in Plant
In plant rate of catabolic process is very slow and waste product are produce in less amount. They are used again in their anabolic process.
Waste Substance of Plant
The substance which are produce in excess amount are
- Water
- CO2 and O2
- Ions
Removal of Water
Extra water is removed from the body of plant by two methods.
Transpiration
The extra amount of water removed in the form of vapor through stomata is called transpiration.
Guttation
When water is removed from plant in the form of drop this process is called Guttation. Guttation occur special opening called hydathods. Guttation take place in those plant which grow in tropical rain forest.
Release of Oxygen and Carbondioxide
- In day time plant used CO2 for photosynthesis process and released O2.
- In night time plant released CO2 and inhale O2 gas.
Ions
Excess amount of ion are deposit into dead cell of plant body such as bark.
Thermoregulation
The maintained the temperature of the body with in a range is called thermoregulation.
Thermoregulation in Plant
The normal range of temperature in plant is 10oC to 35oC. The adaption of plant to low and high temperature are as follows.
Low Temperature
- At low temperature the nature of plasma membrane is changed and produce crystalline structure due to which transport of solute is slow.
- To control this condition plant cell produce unsaturated.
- At freezing point ice crystal are formed in the cell. But the plant of cold region change the composition of solute of cell so ice crystal are not formed in cytoplasm they form in cell wall. This condition is known as freezing tolerance.
High Temperature
High temperature has more harmful than low temperature for plant.
- Due to high temperature all enzyme are denature and metabolic process stop. So plant increase rate of transpiration and cool the body.
- At above 40oC plant produce heat shock protein. They protect the enzyme from destroying.
- In some plant shiny cuticle is present which protest them from high temperature.
- In some plant leaves are reduce in size.
Osmoregulation In Animal
Osmoregulation in Terrestial Animal
In land animals excretion of water take place through body surface so they have develop number of strategies to maintain Osmoregulation.
Water Proof External Covering Epidemics present in reptile, mammal cuticle present in insect which prevent the water loss from their body.
Storage and Excretion of Solid Wastes In birds, reptile and insect store nitrogenous waste uric acid. Uric acid insoluble in water and help to reabsorption of water in cloeca. Uric acid excreted the body in the form of paste and crystal.
Use of Metabolic Water
Some mammal fat is converted into simple compound and during this process water is produce which is reused in the body. Camel, Kangroo used metabolic water.
Storage of Harmful Waste In mammal urea in kidney which is helps in reabsorption of water.
Osmoregulation in Aquatic Animal
Osmoregulation in fresh water animal is maintained by two methods.
1. By Contractile Vacuole
2. By producing dilute urine
1. By Contractile Vacuole
Fresh water unicellular organism have contractile vacuoles. Water with dissolved CO2 and uric acid is collected from the endoplasm into the contractile vacuole, which increase in size up to a maximum and burst released the extra substance in environment. In Amoeba and Paramicium the amount of water and other substance remain in balanced by contractile vacuole.
2. By Producing Dilute Urine
Fresh water fishes have hypertonic body fluid as compare to surrounding water. Fisher released extra amount of water in the form of dilute urine and absorb some essential ion from outside to maintain the salt and water content in the body.
Osmoregulation in Marine Animal
Marine water fishes have hypotonic body fluid than surrounding because sea water have high concentration of salt so these fishes drink water continuously and the salt excreted out along with concentrated urine. They also excrete salt through gills.
Excretion in Animal
In animal removal of nitrogenous waste from the body is very essential. Animal have particular organ to excrete out nitrogenous waste.
Waste Substance of Animal
Animal produce different type of waste substance such as
1. Ammonia
2. Urea
3. Uric Acid
4. Creatinine
5. Hypozenthine
1. Ammonia
- It is a small molecule of gas. Its formula is NH3.
- It is highly soluble in water.
- It is very toxic compound
- It is dissolved in water and removes by simple diffusion method through skin or by urine.
- It is excretory substance of aquatic animal e.g. fishes.
2. Urea
- Urea is less soluble in water.
- Its formula is CO(NH2).
- Urea is very less toxic substance because its 1,00,000 time less toxic then NH3.
- Urea is produce as a result of metabolism in the liver from ammonia.
- This process required energy.
- Urea is the excretory product of mostly land animal like mammals.
3. Uric Acid
- Its formula is C5O3N4H4.
- It is not soluble in water.
- Uric Acid is less toxic than urea.
- Uric Acid released from the body in paste like substance or urete crystal.
- Urid Acid is the excretory product of insect, birds and reptile.
Excretion in Hydra
(Exetory Substance (NH3))
Hydra is a water living animal. In this body the excretory products are produced in the form of NH3. It is excreted out the gastrovascular cavity and then removed from the body along with water.
Excretion in Planaria
(Exetory Organs)
In planaria nitrogenous waste excrete out through skin and special excretory organ called flame call or protonephridia.
Structure of Excretory System and Functions
In the body of planaria there is a system of branch tube like bodies. There are two longitudinal excretory trunks one on either side of the body.
Nephredipores
They open to the out side by small pore called nephredipores.
Flame Cell
Internally these excretory trunk divide and redivide into number of small branches at the end of the branch special cell are present are called flame cell. The flame cells are club-shaped hollow cells. In their internal cavity many cilia are attached which perform movement just like flame of candle.
Functions
All the waste product of main branches absorb by flame cell because the movement of cilia of flame cell. When the excretory product come into the longitudinal excretory system they are removed out of the body through the nephrediopore.
Excretory Organs
The excretory system of earthworm consist of small, coiled tubes called Metanephredia. It is present in each segment.
Structure of Nephredium
Each Nephredium consist of three part.
1. Nephrostome
It is a rounded, ciliated funnel with the opening.
2. Bladder
Main body of nephridum consist of coiled tubular part and wide part called bladder.
3. Nephridiopore
The bladder opens outside by a small pore on the skin are called nephridiopore.
Excretion
As fluid moves along the tubule, epithelium reabsorbs the salt from lumen and send to blood vessels surrounding the nephridium. The left over appears as urine containing nitrogenous waste.
Excretion in Cockroach
Excretory Organs
Cockroach have special tube like excretory structure are called "Malphighian Tubules". It is present between the mid gut and hind gut. It is embedded in the blood.
Excretion
Malphighian tubules absorb all nitrogenous waste from blood and pour them into illium. The latter part of tubules reabsorbs important substance. The uric acid when come into rectum, it also reabsorbs water and salt, so uric became almost dry then it is excreted out of the body.
Liver
Liver is the large raddish brown glandular organ which is central station of metabolism and consequently the body is central metabolism clearing house.
Location
Liver located in the abdomen just below the diaphragm.
Functions of Liver
Liver is the main homeostatis organ which perform several function.
1. Metabolism of CHO and LIPIDS
- Liver is the center of metabolism. Is take part in metabolism of carbohydrate and lipid. It regulates the amount of glucose into the blood. Excess glucose is converted into glycogen, which is reserve food. It amount of glucose is decrease in the blood glycogen is broken into glucose. Glycogen is reduce than liver convert amino acid into glucose.
- Liver also help in oxidation of lipid. It is converted blood lipid into simple fat which is stored in the body.
2. Deamination and Urea Formation
Excess of protein can not be store in body. Protein are change into amino acid. Amine group is removed from the amino acid this process is called deamination of form NH3. Amonia combine with CO2 and convert into urea by a cycle called ornithine cycle.
3. Production of Bile
Liver produce a secretion called Bile. It is yellowish green alkaline substance. Bile contain bile pigment biliverdin, bilirubin, salt such as sodium-glycocholate, Na-taurocholate, Cholesterol, Phospholipid and mucous.
Functions of Bile
- Bile neutralizes the acidic food
- It kills the germs
- It takes part in the emulsification of fat.
4. Detoxification
Liver convert toxic substance into non toxic substance this process are called detoxification.
For example a compound hydrogen peroxide H2O2 is a harmful compound. The liver secrete on enzyme catalase which convert H2O2 into H2 and O2 and became non poisonous substance.
5. Formation of Cholesterol
Liver also forms cholesterol which is necessary for the body. Its extra amount is always excreted along with water.
5. Formation of Cholesterol
Liver also forms cholesterol which is necessary for the body. Its extra amount is always excreted along with water.
6. Thermoregulation
Liver helps in regulation of body temperature by continue supply of blood and metabolic process.
7. Storage of Vitamins
Liver stores vitamins such as A1B and D.
Urinary System in Human Being
Urinary system of man consist of
Kidney
Kidneys are pair of dark red bean shaped structures which are attached to the dorsal wall of the abdominal cavity.
- Kidney are covered by a membrane are called peritoneum.
Ureter
Urine leaves the kidney through a pair of duct called Ureter.
Bladder
The ureters of both kidney drain into pear shaped thin walled structure are called bladder.
Urethra
Urine leaves the body during urination from the bladder through a tube called Urethra.
Sphincter
Sphincter muscles near the junction of the urethra and bladder control the urine in bladder.
Kidney
Kidney are a pair of dark red bean shaped structures which are attached to the dorsal wall of the abdominal cavity.
Structure of Kidney
Internally kidney consist of two part
1. Cortex is the outer and darker region.
2. Medulla is the inner and lighter region in the kidney. It contain many cone like structure are called pyramids.
Nephron
The basic structural and functional unit of kidney are called Nephron.
OR
Kidney consist of million of microtubules are called Nephron.
Structure of Nephron
Each nephron is sub-divided into
1. Renal Corpuscle
2. Renal Tubule
1. Renal Corpuscle
Each renal corpuscle is divides into two
i. Bowman's Capsule
ii. Glomerulus
i. Bowman's Capsule
In each nephron inner end forms a cup-shaped swelling called Bowman's capsule.
ii. Glomerulus
Each bowman's capsule have a ball of capillaries called glomerulus. Glumerulus circulates blood through capsule as it arrives through Aferent Arteriole. Blood carried away from the capsule by a small vessel called Efferent Arteriole. The blood vessel sub divide again into another network of capillaries called Peritubular Capillaries.
2. Renal Tubule
Bowman capsule continuous as extensively tubular system.
i. Proximal Convoluted tubule
ii. Loop of Henle
iii. Distal convoluted tubule
iv. Common collecting duct
i. Proximal Convoluted Tubule
Bowman capsule gives out a coiled tubule called Proximal Convoluted Tubule.
ii. Loop of Henle
The proximal convoluted opens into a U-Shaped structure called loop of Henle. Loop of Henle consist of descending and ascending limbs.
iii. Distal Convoluted Tubule
The ascending limb of loop of Henle opens into another convoluted tubule called Distal Convoluted Tubule.
iv. Collecting Tubules
Distal tubule empties into collecting tubules which open into pelvis.
Functions of Kidney
Urine formation take place in these following steps:
1. Ultra Filtration
2. Selective Reabsorption
3. Tubular Secretion
4. Counter Current Exchange
2. Selective Reabsorption
All the important constituent of the glomerular filtrate are reabsorbed when filtrate pass in tubular system.
- Prominal convoluted tubule reabsorb salt amino acid, glucose and water.
- Descending limb of loop of Henle reabsorb Na and Cl inter in the interstial fluid. Na and Cl reabsorbed by active transport. Water is not reabsorb.
- Distal convoluted tubule have hypotonic solution due to high concentration of water. In this part by the action of hormones concentration of various salt is adjust.
3. Tubular Secretion
Tubular section is also very important process of excretion. The tubular epithelium also secrete substances into teh lumen this secretion is very selective and mainly of hydrogen into balance pH value of the filtrate passing through the tubule.
4. Counter Current Exchange
The exchange of solute and water in the medulla of kidney is called counter current exchange. There are two counter exchanges:
i. Counter Current Multiplier
ii. Counter Current of Vasa Recta
i. Counter Current Multiplier
When the filtrate passes through the descending limb of loop of Henle water is reabsorbe due to this process the filtrate became hypertonic.
ii. Counter Current of Vasa Recta
The blood vessels which run parallel to the loop of Henle are called Vasa recta. Through these blood vessels only about 10% of blood of kidney passes very slowly. This blood supplies oxygen and nourishment to the cell of medulla and carries away the reabsorb water from the filtrate. The system is regulate and maintained properly.
Reabsorption in the Nephron
Types of Nephron
There are two type of nephron
1. Cortical Nephron
2. Juxtamedullary Nephron
1. Cortical Nephron
The nephron which have small length of loop of Henle and only present in cortex region of kidney are called Cortical Nephron.
2. Juxtamedullary Nephron
These nephron have long loop medullar of kidney reabsorb more water are called juxtamedullary nephron.
Effect of Hormones on the Working of kidney
Certain hormones control the working of kidney.
1. Andiurelic Hormones (ADH)
2. Aldosteron Hormones (AH)
3. Parathormon Hormone (PTH)
1. Antidiurelic Hormones
Pituitary gland secrete ADH. It is also called vasopressin.
Functions
Hormones helps in reabsorption of water. Hormone is produce at the time of dehydration. It causes shortage of water in the body due to rapid loss of water. The osmotic pressure of blob increases. This hormone helps to balance the amount of water.
2. Aldosteron Hormones
Outer part of adrenal cortex secreted aldosteron harmine.
Functions
It control the concentration of Na+ in the bosy fluid. It increase the reabsorption of sodium ion in nephrone.
3. Parathormon Hormones
Parathyroid gland secrete parathormone.
Kidney Problem
Kidney is not perform properly due to different reason are called Kidney problem or Kidney disease.
There are many problems of kidney
1. Kidney Stone
2. Renal Failure
1. Kidney Stone
Stone solid materials are found in the kidney called Kidney Stone.
Causes
Kidney stones are caused by metabolic disease.
70% of kidney stone are formed due to calcium oxalate and phosphate oxalate. Oxalate are produced in the metabolic process and added in the urine and deposit in kidney change into stones. Oxalates are present in green vegetables and tomatoes therefore may be the source of oxalate stone.
Infective Stone
20% stone are called as infective stone. Infective stone consist of combination of calcium, magnesium and ammonium phosphate.
Uric Acid Stone
5% stone are formed in uric acid.
Cure
Lithotripsy
The lithotripsy is used for non surgical removal of kidney stone. It is a technique used to break up stones that form in the kidney, ureter or gall bladder.
Method
There are several way to do it although the most common is shock wave lithotripsy or ultrasonic lithotripsy. High concentration X-Ray or ultrasound are directed from a machine outside the body to the stone inside. The shock waves break the stone in tiny pieces or into sand which are passed out of the body in urine.
Renal Failure
Sometimes the working of kidney is badly damaged due to certain reason or infection. They are not able to filter the harmful nitrogenous substance it is called renal failure. In such condition the harmful substance remain in blood.
Symptoms
- Nausea
- Vomiting
- Loss of appetite
- Weakness
- Difficulty in breathing
Treatment of Kidney Failure
Dialysis
A technique to remove nitrogenous wastes particularly the urea from the blood of the patient is called Dialysis.
Type of Dialysis
There are two types of dialysis
1. Haemodialysis
2. Peritoneal Dialysis
1. Haemodialysis
Haemodialysis means "Cleaning the blood". In this procedure blood is circulated through a machine which contains a dialyzer also called on artificial kidney.
Dialyzer has two spaces separated by thin membrance and dialysis fluid on the other. The waste and excess water pass from the blood through the membrane into the dialysis fluid. Dialysis take place 6 to 10 hours and 3 time in a week.
2. Peritoneal Dialysis
Abdomen has a peritoneal, lined by a thin epithelium called peritoneum. Peritoneal cavity is filled with dialysis fluid that enters the body through a catheter. Excess water and wastes pass through the peritoneum into the dialysis fluid. This process is repeated several times in a day.
Kidney Transplant
Dialysis may be used as temporary measure. In high degree renal failure also called as Uremia or end stage renal disease, the dialysis is done endlessly thus the surgical transplantation of matching donor kidney is only the option left as the permanent treatment.
Thermoregulation in Animal
Temperature Classification of Animal
According to the body temperature animals are divides into two group.
1. Poikilotherms (Cold Blooded)
2. Homeotherms (Warm Blooded)
1. Poikilotherms
Animal cannot maintain their body temperature and it can be changed accordingto the climate are called Poikilotherms.
Example
Amphibians, Reptile, Fishes.
2. Homeotherms
Animal can maintain their body temperature. It does not changed according to their environment are called Homeotherm.
Example
Birds, Mammals
Many poikilotherm can maintain their body temperature and homeotherm do not maintain their body temperature always. So there terms are changed.
Modern Classification of Animal
The modern classification of animal according to the body temperature.
1. Ectothermic
2. Endothermic
3. Heterothermic
1. Ectothermic
Ecto mean outside thermic mean heat so those animal obtained heat energy from their environment are called Ecotothermic.
Example
Invertibrate, Fish, Amphibian and Reptile.
2. Endothermic
Endo mean inside thermic mean heat so those animals use internal energy which is produced during their metabolism.
Example
Mammalia, Birds and Some Fishes.
3. Heterothermic
Those animals are able to maintain their body temperature with certain variation, so their body temperature can be changed upto certain limits are called Heterothermic.
Example
Bat, Humming birds.
Method of Thermoregulation in Animals
In animal thermoregulation occurs by two ways.
1. Behavioral Regulation
2. Physiological Regulation
1. Behavioral Regulation
When temperature is maintained by the activity of animal body, it is called behavior regulation, such as animals change their position to increase or decrease the temperature.
2. Physiological Regulation
When temperature of the body is maintained by inter-physiological process it is called physiological regulation, such as change in blood circulation etc.
Thermoregulation in Cold Temperature
In cold temperature animal regulate their body temperature by two methods.
1. Physiological Process
2. Behavioral Process
1. Physiological Regulation
This is the internal process of the body to maintain body temperature. It take place by two way
i. Non-shivering thermogenesis
ii. Shivering thermogenesis
i. Non-Shivering Thermogenesis
Hormones trigger the heat production as do thyroid hormones are called Non-shivering thermogenesis.
Mechanism
In this mechanism heat is produce by three methods.
- Erection of hairs
- Reduction of blood flow toward skin
- Sub cutaneous fat accumulation
In cold season the hair become in erect position. In furry animals air is trapped between the space of hairs and loss of body heat is stopped.
Reduction in Blood Flow toward Skin
In cold season the blood vessels of skin are reduced. It is called Vasoconstriction. Due to this process blood flow towards skin become slow and loss of heat through skin is reduced.
Sub Cutaneous Fat Accumulation
In mammals below skin fat is deposited in adipose cell. It prevent the loss of body heat. It is common in aquatic animals such as Seal, Whale.
ii. Shivering Thermogenesis
The rate of heat production is increased y increased muscle contraction by movement or shivering so called as shivering thermogenesis.
Mechanism
In very cold weather shivering occur in the muscles of the body. It produce heat Rate of Metabolism become faster. In this mechanism hormones are involved one hormone adrenaline is produce by adrenal gland. It increases the supply of glucose in blood so respiration become fast and energy is produce.
Thyroid gland also secreted thyroxin hormone in blood. This hormone also increased respiration to produce heat.
2. Behavioral Process
In this mechanism the animals produce heat by their body activities.
Movement toward Hot Place
Animals move toward hot places during cold season.
Gathering of Animals
The animals come close to each other, so energy is produced.
Use of Warm Cloths
Man used warm clothes for protection and to get heat.
Thermoregulation in Hot Temperature
In hot season the animal produce less heat and also released heat from their body. It take place by two method.
1. Physiological Mechanism
2. Behavioral Mechanism
1. Physiological Mechanism
This process take place by following method.
Less Fats Deposition
In hot season fat is not deposit in below the skin. It loss the body heat.
Increase in Blood Flow toward Skin
In hot season the blood vessels of skin are dilated and vasodialation occur to released body heat.
Softness of Hair
Hair of skin not erect in hot season not prevent the loss of heat energy.
Sweet Gland
Sweet glands become active and water is excreted out through skin. The blood becomes cold and internal temperature is maintained. It is called physiological temperature regulation.
2. Behavioral Mechanism
In this mechanism the animal released heat by their body activities.
Movement toward Cold Places
Animal move from hot to cold places. They remain in shade or moist place to reduce their body heat.
Use of Thin Clothes
Man use thin clothes during summer season.
Role of Brain in Thermoregulation
The body temperature regulation in human is based on complex homeostatic system facilitated by feedback mechanism.
The Control Center
The homeostatic thermostate is present in the hypothalamus, a brain part. It respond to the changes in the temperature above and below 37oC.
Warm Temperature
Incase of increase in temperature above 37oC certain warm temperature sensitive thermoreceptors in skin, hypothalamus and other parts of nervous system send the signals to the system that increase the blood flow to the skin and also cause sweat gland activation and sweat is evaporated for the cooling.
Cold Temperature
In cold temperature, the cold receptor send the impulse to hypothalamus to inhibit heat loss mechanism and activate the heat conservation mechanism.
Fever
When the temperature of the body is increased beyond a set point it is called Fever or Pyrexia.
Cause of Fever
The main cause of fever is the viral or bacterial infection. These germs in blood vessels produce a chemical substance called pyrogen. It increases the body temperature than normal.
Importance
- Fever helps to kill the germs
- It indicates any abnormal condition in the body or infection.
Reproduction
Reproduction
The process through which organisms produce young ones of their own kind to maintain their species are called as Reproduction.
Types of Reproduction
There are two types of reproduction.
1. Asexual Reproduction
2. Sexual Reproduction
1. Asexual Reproduction
The type of reproduction in which fusion of gamets does not take place and requires only a single parental organism and the offspring produced are exact copies of their parents. This type of reproduction is called Asexual Reproduction.
Asexual Reproduction of Plants
There are two methods of asexual reproduction in plants.
1. Natural Method of Asexual Reproduction
2. Artificial Method of Asexual Reproduction
1. Natural Method of Asexual Reproduction
In nature, plants reproduce asexually by following methods.
i. By Spores or Sporulation
ii. Vegetative Propagation
iii. Apomixis
i. By Spores or Sporulation
During alternation of generation plant produce haploid cell by meiosis called Spores. Each spore can develop into new organism without fertilization. The process of formation of unicellular spores is called Sporulation.
Example
Sporulation occurs in bacteria, protozoans, algae, fungi, mosses and fern as well as plants.
ii. Vegetative Propagation
The process which involves the separation of the part of the parent plant which then develop into new plant is called as Vegetative Propagation.
OR
When a new plant develops from tissue, organs of a plant or outgrowth of a plant. This type of reproduction is called Vegetative Propagation.
Process
In this process a plants part is separated which develops into new plant such as stem, leaves roots or buds may take part in the formation of new plant.
Methods of Vegetative Propagation
There are various method of propagation of plant by vegetative reproduction for improving crops, orchads and ornamental plants are as follows
i. By Cutting
ii. By Grafting
i. By Cutting
In this method stem or branch is cut from the plant. At the cut end of the shoot a mass of dividing undifferentiated cells called a callus forms and then adventitous roots develop form the callus. If the shoot fragment includes a node, then adventitous root forms without callus stage.
Example
Sugar cane, sweet potato and rose can be propagated by cutting. In raspberry and black berries root cutting are also used for artificial vegetative propagation.
ii. By Grafting
This is a technique whereby a branch from a desired variety of plant is joined to another plant with well established root system. The plant from which the branch is taken is called Scion and the plant to which it is joined is called Stock. The two plants involved are normally the different varieties of same species.
Example
Orange, lime and mango can be propagated by grafting.
iii. Apomixis
The modified form of asexual reproduction in which seeds are formed without fertilization is called Apomixis.
Mechanism
In apomixis, a diploid cell in the ovule gives rise to the embryo without any fertilization and the ovules mature into the seeds.
Example
In Dandelions and other plants seed formation take place without fertilization.
2. Artificial Method of Asexual Reproduction
In plant vegetative reproduction is performed by artificial method, which are as follows
i. Tissue Culture or Test Tube Cloning
ii. Protoplast Fusion Technique
i. Tissue Culture or Test Tube Cloning
Tissue culture or cloning is a special technique which is used to produce varieties of plants. By this technique, a group of genetically identical offspring produced by asexual method called Clones.
Procedure
In this method, pieces of tissues are cut from the parent plant or from a single parenchymatous cell in a medium containing all the nutrients and hormones.
The culture cells divide and form an undifferentiated Callus.
The callus then produces root and shoot with fully differentiated cells.
The test tube plant can be transferred to soil where they continue their growth.
Application
In plants tissue culture is also used in genetic engineering. To introduce new genes in plant body pieces of tissue or cells are used. By this technique, we produced a new variety of plant by introducing new DNA molecule.
Example
By cloning many thousand plants are produced from one plant. This method is used in Orchards and pinus trees to obtain wood.
Advantages of Tissue Culture
The main advantages of tissue culture are as follows
i. Development of Strong Plant: By this technique plants of Agriculture and horticulture are produced. These plants are strong than other plants produced by seeds.
ii. Development of Similar Plant: By this technique plants of similar character are developed.
iii. Development of Defence System in Plant: These plants have developed defence mechanism against any disease.
iv. Production of Useful Chemicals: By this technique, many useful chemicals are obtained such as shikonin (a dye used in silk and in the treatment of injuries caused by burning.
Disadvantages of Tissue Culture
There are also some disadvantages of tissue culture where are as follows
i. Production of Sterile Plant: The plant produced by this technique may be genetically sterile, do not reproduce by sexual method.
ii. Variation in Chromosome: This technique may cause change in the structure and number of chromosome.
ii. Protoplast Fusion Technique
Another technique known as protoplast fusion technique is developed to produce new varieties of plants.
Procedure
In this technique, outer cell wall is removed around the protoplast. After protoplast of one or more cells are fused together, then their protoplast are for culture. These protoplast produce a wall around them, then they are change into new plant. Protoplast of either same or different species may used for this technique.
Example
In potato and wild night shade plant this technique is used.
2. Sexual Reproduction
The type of reproduction in which fusion of gametes (sperm and ova) take place and two parents (male and female) are involved is termed as Sexual Reproduction.
Sexual Reproduction in Plant
In plants sexual reproduction takes place by three methods.
i. Isogamy
ii. Oogamy
iii. Heterogamy
i. Isogamy
The simplest type of sexual reproduction in which two morphologically similar gametes take part in fertilization to produced zygospore which then develop into new plant is called Isogamy.
It is also known as conjugation which means marriages of equals.
Example
This process occurs in algae and lower plants.
ii. Oogamy
The type of sexual reproduction in which a flagellated motile sperm fertilizes with non motile egg to produced a diploid zygote which then develop into new individual is called Oogamy.
Example
Some species of algae undergoes Oogamy.
iii. Heterogamy
The type of sexual reproduction in which two different structure gamets fused i.e. non flagellated large size female gamete fuses with small size flagellated male gamete to produced zygote which then develop into new plant is called Heterogamy.
It is also known as anisogamy.
Example
In higher plants such as bryophyte, heterogamy is present.
Germination
The process in which dormant or sleeping embryo awakes up renews its life and develops into a seeding is called as Germination.
OR
The breaking of dormancy of seed to produce seedling is called Germination.
Kinds of Germination
Seed can germinate into three ways i.e.
1. Epigeal Germination
2. Hypogeal Germination
3. Viviparous Germination
1. Epigeal Germination
Epi => above, geo => earth
The kind of germination in which cotyledons came above the soil due to rapid growth of hypocotyl is called Epigeal Germination.
Example
Caster oil seed, tomato, cotton etc.
2. Hypogeal Germination
Hypo => below, geo => earth
The kind of germination in which cotyledons remain under the soil due to rapid growth of epicotyl is called Hypogeal Germination.
Example
Maize-grain, Pea-gram etc.
3. Viviparous Germination
The special of germination in which seed germinates within fruit is called Viviparous Germination.
Process
The fruit is still attached to parent plant. Redicle comes out of the fruit which becomes swollen and heavy due to increasing weight the seedling gets detached and falls vertically into the soft mud gets embeded and starts growing.
Example
Rhizophora, coconut, date palm etc.
Seed
Seed may be defined as
A ripened ovule or a part of a plant body in which embryo lives in dormant condition is called Seed.
Structure of Seed
Structure of seed can be divided into two parts
1. External Structure
2. Internal Structure
1. External Structure
Externally seed consists of following parts
Seed Coat
The seed is covered from outside by a coat called Seed Coat.
The seed coat is formed by integuments. It is made up of two layers.
Testa
The outer thicker layer is called Testa.
Tegmen
The inner thin layer is called Tegmen.
Chromosomes as Carrier of Genes
Genes are small bodies found in the chromosome.
Chromosome are considered as the carrier of genes.
The chromosomes can be separately identified visually but the genes are very small units. And so far have not been seen even with the best microscope.
The chromosome and gene behave as hereditary units but the genes can not be considered outside the chromosome.
At the time of meiosis, the separation of homologous chromosomes takes place which result in the segregation of gene pairs.
In the genotype of every individual one member of each pair of genes is contributed by one parent and the other by the other parent.
Chromosomal Theory of Heredity
Introduction
The chromosomal theory of inheritance was first formulated by the American Biologist "Walter Sutton" in 1902.
Postulates
The main postulates of this theory are as under
1. Hereditary Materials
Reproduction involves the initial union of only two cells, egg and sperm. If Mendel's model is correct then these two gametes must make equal hereditary contributions. Sperm, however contain little cytoplasm, therefore the hereditary material must reside within the nuclei of the gametes.
2. Segregation of Chromosomes
Chromosomes segregated during meiosis in a manner similar to that exhibited by the elements of Mendel's model.
3. Number of Chromosome
Gametes have one copy of each pair of homologous chromosomes, diploid individuals have two copies.
4. Independent Assortment
During meiosis each pair of homologous chromosomes orients on the metaphase plate independent of any other pair.
Objection
The objection on chromosomal theory of hereditary is that when there is independent assortment of chromosomes in meiosis, the number of factors (genes) is more than the number of chromosomes. This is considered as a fatal objection about Sutton's theory.
Evidence
The material which transmits the parental characters into the coming generation is called Hereditary Material.
Fredrick Griffith's Experiment
Introduction
Fred Griffith in 1928 provided the evidence of hereditary material in bacteria.
Experimental Material
He was working on strains of steptococcus pneumoniae, which occurs in two distinct different forms.
R-Type
Rough surfaced, non-capsulated bacteria, without the capability of producing pneumonia.
i.e. non-virulent
S-Type
Smooth surfaced, capsulated bacteria, with the capability of producing pneumonia i.e. virulent.
Steps of Experiment
He observed that when the injected R-type bacteria in the mice, there was no ill effect.
When he injected the S-type, they proved to be fatal.
He also observed, when he injected both the bacteria separately after killing them by heating under high temperature, the mice did not develop the disease.
He also observed that, when the injected the living R-type with heat-killed S-type, there was a high morality among the mice.
Conclusion
Fred Griffith concluded that the R-type bacteria gained genetic property of S-type inactive bacteria when they kept together, so R-type bacteria converted into virulent S-type by the activity of DNA. Hence by this experiment, it can be proved that DNA is a genetic material.
A Very, Macleod and McCarty's Experiment
Introduction
In 1944, after a decade of research, Oswald Avery, Maclyn McCarty and Colin Macleod discovered that the transforming agent had to be DNA.
Experiment
They performed various experiments and found out that the only substance, which carried the transforming capability, was DNA because if the enzyme deoxyriba-nuclease was added to the bacteria, the transforming capability was lot.
Hershey and Chase's Experiment
Introduction
In 1952, Hershey and chase performed experiment to proof that DNA is a hereditary material.
Experience at Material
Hershey and chase labeled protein coat and DNA of Bacteriophage separately. Protein coat labeled with radioactive sulphur and DNA with radioactive phosphorus. These two viruses use to attack bacterial cells.
Steps Experiment
Hershey and chase observed that if cultures of bacteriophage are labeled with radioactive phosphorus [P32 labeling DNA] or with sulphur [S35 for labeling protein coat].
bacteriophage is ruptured, the DNA is released and treated with deoxyribsonucleas, the DNA breaks up into fragments in the solution.
The empty protein coats of the ruptured membrane appear as coats all the P32 or S35 were made to inject bacteria and multiply by the help of special technique, all the S35 labeled protein were removed.
The new phage formed contained only P32 indicating the presence of DNA molecule.
Conclusion
The conclusion appears similar to the transforming principle in bacteria, showing that DNA is the genetic material in phage, transmitted from one generation to the next.
Watson and Crick's Model of DNA
Introduction
James Watson and Francis crick, in 1953 proposed structure of the DNA molecule.
Structure of DNA
Watson and Crick suggested a ladder like organization of DNA.
1. Double Helix
Each molecule of DNA is made up of two polynucleotide chains which twisted around each other and form a double helix.
2. Backbone of DNA
The uprights of the ladder are made up of sugar and phosphate parts of nucleotide and the rungs are made up of a paired nitrogenous bases.
3. Pairing of Bases
The pairs are always as follows
Adenine always pairs with thymine and cytosine with Guanine.
The two polynucleotide chains are complimentary to each other and held together by hydrogen bonds.
Hydrogen Bonding
There are two hydrogen bonds between Adenine and Thymine (A=T) and three between Cytosine and Guanine (C≡G).
Distance
Both polynucleotide strands remain separated by 20 Aº distance.
The coiling of double helix is right handed and complete turn occurs after 34 Aº. In each turn 10 nucleotide pairs are present, therefore the distance between two pairs is about 3.4 Aº.
Genes - The Unit of Hereditary Information
Introduction
Archibald Garrod discovered in 1902, that certain diseases were more prevalent among some families and were inherited as a recessive Mendelian trait.
Alkaptonuria
Alkaptonuria is a disease in which the urine contained a substance called "Alkapton" now known as "Homogentisic acid" which was immediately oxidizes to black when exposed to the air.
Causes
He suggested that this disease occurred due to absence of an enzyme, which could break the "Alkapton" down to other products so it would not build up in the urine.
He proposed that the condition was "An inborn error of metabolism" which is occurring due to changes in the hereditary information, which must have occurred in one of the ancestors of the affected families.
Conclusion
He concluded that the inherited disorders might reflect enzyme deficiencies.
Genome
Definition
The total genomic constitution of an individual is known as Genome.
Example
In a bacterial cell, a single circular chromosome along with plasmid is genome of bacteria, while in a human being all twenty two pairs of autosome along with a pair of sex-chromosomes constitute genome.
Replication of DNA
Definition
The mechanism in which DNA prepares its copies is called DNA replication.
OR
When the formation of new DNA molecule takes place in the cells without any change, it is known as Replication of DNA.
Semi Conservative Replication
Definition
The type of replication in which new daughter double helical duplex contain one stand old and another newly synthesized is called Semi Conservative Replication.
The Meselson Stahl Experiment
Introduction
Mathew meselson and Frank Stahl performed experiments to test the semi-conservative method of DNA replication.
Experiment
They grew bacteria in a medium containing Nitrogen-15 (N15), a heavy isotope of the nitrogen.
The DNA after several generations became denser than normal because the entire bacterial DNA now contained Nitrogen-15 (N15).
They then transferred the bacteria into a new medium containing lighter isotope Nitrogen 14 (N14) and analyzed the cultures for changes in the DNA.
At first DNA, which the bacteria synthesized, was all heavy.
After one round the density of the DNA fell exactly to the value one half between the all heavy isotope DNA and all light isotope DNA.
Result
This showed that after one round of replication, each of the daughter DNA duplex contained one strand of heavy isotope, after two rounds half contained none of the heavy isotope strand to form light duplex and half contained one of the heavy strand isotope.
It was now confirmed that the semi conservative method of the replication of DNA replication was true.
One Gene One Enzyme Hypothesis
Introduction
George Beadle and Coworker Edward L. Tatum proved that the information coded within the DNA of a chromosome, is used to specify particular enzymes.
Method of Study
Beadle and Tatum created Mandelian mutation in the chromosomes of the fungus called Neurospora by the use of the x-rays.
They studied the effect of the mutations caused by them and suggested "One Gene One Enzyme Hypothesis".
Choice of Material
They choose the bread mold, neurospora crassa as an experimental organism. It had a short life cycle and was easily grown on a defined medium, containing known substances, such as glucose and NaCl.
The nutrition of Neurospora could be studied by its ability to metabolize sugars and other chemicals the scientist could add or delete from the mixture of the medium.
Production of Mutations
They induced mutations in Neurospora spores by using x-rays.
The mutated spores were placed on complete growth media enriched with all necessary metabolites, so keeping the strains alive because the strains were deficient in producing certain compounds necessary for fungus growth due to damaged DNA by earlier irradiation, hence called Mutants.
Identification of Mutant Strains
To test the mutations, they grew the mutated strains on the animal media containing sugar, ammonia, salt, a few vitamins and water.
A strain that had lost the ability to make a necessary metabolite, failed to grow on such media.
Using this approach, they succeeded in identifying and isolating the different mutants.
Identification of Specific Mutations
To determine the specific nature of each mutation, they added various chemicals to minimize media, to make the strains grow.
Using this technique, they were able to pinpoint the biochemical problem and thus the genetic deficiency of the mutants.
Many of the mutants were unable to synthesize a single amino acid or a specific vitamin.
If a spore lacked the ability to synthesize a particular amino acid, such as Arginine, it only grew if the Arginine was added in the growth medium. Such mutants were called as arg mutants.
Chromosome mapping studies on the organism facilitated their work and they mapped three areas clusters of mutant Arginine genes.
For each enzyme in the arginine biosynthetic pathway, they were able to isolate a mutant strain with a defective form of that enzyme and mutation always proved to be located at one of a few specific chromosomal sites, different for each enzyme.
Conclusion
They concluded that genes produced effects by specifying the structure of enzymes and that each gene encodes the structure of a single enzyme. This was called "One Gene One Enzyme Hypothesis".
RNA
Definition
The single stranded helical polynucleotide contain ribose sugar and uracil instead of thymine is called RNA.
Location
RNA is formed in the nucleus (in nucleolus 10%) as well as in the cytoplasm (90%).
Types of RNA
There are three types of RNA.
1. Ribosomal RNA (rRNA)
The class of RNA found in ribosome is called ribosomal RNA.
Function
During polypeptide synthesis it provides the site on the ribosome where the polypeptide is assembled.
2. Transfer RNA (tRNA)
A second class of RNA is called transfer RNA is much smaller. Human cell contains more than 40 different kinds of tRNA molecules.
Functions
During polypeptide synthesis tRNA molecules transport the amino acid into the ribosome for the synthesis of polypeptide chain.
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